Summary

cron.scheduler treats webhook as a valid delivery platform during target resolution, but _deliver_result() later rejects the same target as unknown platform 'webhook'. This means a configured deliver="webhook:..." target can pass earlier validation but can never actually deliver.

Affected code

• cron/scheduler.py:44-48 — _KNOWN_DELIVERY_PLATFORMS includes "webhook"
• cron/scheduler.py:148-158 — resolver accepts platform names in that allowlist
• cron/scheduler.py:240-258 — platform_map omits webhook
• cron/scheduler.py:258-262 — returns unknown platform 'webhook'

Why this is a bug

The same module advertises and resolves webhook as a supported delivery platform, but the actual delivery implementation cannot map it to Platform.WEBHOOK. That is an internal schema mismatch, not just a missing optional feature.

Minimal reproduction

import os
import pathlib
import tempfile
from cron.scheduler import _deliver_result

with tempfile.TemporaryDirectory() as td:
    os.environ["HERMES_HOME"] = td
    pathlib.Path(td, "config.yaml").write_text("platforms:\n  webhook:\n    enabled: true\n")
    job = {"id": "j1", "deliver": "webhook:any-target"}
    print(_deliver_result(job, "hello"))

Actual output:

unknown platform 'webhook'

Expected behavior

• If webhook is in _KNOWN_DELIVERY_PLATFORMS, _deliver_result() should map it and attempt delivery.
• Otherwise the resolver/allowlist should reject webhook earlier instead of accepting an impossible target.

Actual behavior

• The job is accepted as a webhook target, then later fails with unknown platform 'webhook'.

Suggested investigation

Add webhook to the platform_map (if delivery is supposed to work) or remove it from _KNOWN_DELIVERY_PLATFORMS / target resolution until a delivery path exists. Add a focused regression test for deliver="webhook:any-target".